Download Law of Conservation of Matter and Energy

2. Law of Conservation of Matter and Energy
Common chemistry and measurement terms:

Mass: is the measure of how much matter is an object
o Give the example of mixing baking soda and vinegar in a flask with
a balloon over the top of the flask to create a closed system (where
the chemical reaction is contained in one area). The mass of the
flask was 25.6g after the reaction the mass of the flask was 23.2 g.

THINK ABOUT IT Was matter destroyed in this
experiment? Explain
Answer: No it just changed states from a liquid to a gas.
Matter cannot be created or destroyed Conservation of
Matter
1) Phase Changes: Solid, Liquid and Gas
a. Melting: S-L
c. Condensation: G-L
b. Evaporate: L-G
d. Freezing: L-S
2) Identify the state of change and describe whether you are “adding: or “taking” away
energy.
a. Melting: S-L adding/ taking away energy
b. Evaporate: L-G adding/ taking away energy
c. Condensation: G-L adding/ taking away energy
d. Freezing: L-S adding/ taking away energy
OAT Science Lesson 3
1
The law of conservation of mass states that the mass of the reactants in any chemical
equation equals the mass of the products. The products of a chemical reaction usually
look different from the reactants. If a gas is produced, for example, you may not see it.
Yet its mass must be included as part of the total mass of the products. It also may show
up as bubbles or affect the pressure in a closed container.
The law of conservation of mass is an important law of chemistry and holds true for
all chemical reactions.
1) The instructions for an experiment direct the students to put a liquid into a beaker
and use a hot plate to heat the liquid to 100° C. Describe two safety precautions
the students need to take while heating the liquid. Describe the movement of
particles of the liquid once it reaches 100° C and the phase change. (4 Points)
Answer:
Describe Safety Precaution 1
Describe Safety Precaution 2
Wear lab apron, safety goggles
Long hair should be tied back
Use heat resistant gloves to pick up the
beaker/thermometer
Don’t touch the hot plate
Describe Movement
Describe/ Identify Phase Change
Particles Liquid – Gas particles are speeding
up
Liquid to a gas (boiling or evaporation)
2) A glass of ice water sits outside in the sunlight, completely full. After about an
hour there is no ice left. After three hours the glass of water is only half full.
Describe what happened to the other half of the water, using the idea of
conservation of matter and phase changes. (2 points).
2
Answer:
Describe Conservation of Matter
Describe phase change
Conservation of Matter: Matter cannot
S L  G The ice is change from a solid to a
be created nor destroyed but only
liquid (water). The heat from the sun is change the
changed from one phases to another
liquid to a gas (Water vapor) by evaporating it
into the atmosphere. So therefore it is neither
being created nor destroyed it just changes from
one phase to another.
Transferring Energy
Everything we do is connected to energy in one form or another. Energy is one of
the most fundamental parts of our universe. We need energy to live and move
around, and machines need energy in order to function. We use energy to do work.
Energy lights our cities. Energy powers our vehicles, trains, planes and rockets.
Energy warms our homes, cooks our food, plays our music, and gives us pictures on
television. Energy powers machinery in factories and tractors on a farm. Energy
from the sun gives us light during the day. It dries our clothes when they're
hanging outside on a clothes line. It helps plants grow. Energy stored in plants is
eaten by animals, giving them energy.
But what exactly is energy? Energy is defined as: "the ability to do work."
Energy takes a lot of different forms, like heat, light and sound, as well as the
chemical energy stored in food and the mechanical energy of moving objects.
In 1905, physicist Dr. Albert Einstein formulated the Law of Conservation of Mass
and Energy, which basically states that energy cannot be created or destroyed —
it just changes form. In other words, whenever the amount of energy in one place
decreases, the energy in another place increases by an equal amount. This energy is
3
transferred continually from one object to another and can be converted from one
form to another along the way.
Two classifications of energy are
potential energy and kinetic energy.
Potential energy is stored energy either in
position or form. So, any stored energy
waiting to be used is called potential
energy. For instance, water held in a
reservoir behind a dam is currently at
rest. This is potential energy. On the
other hand, opening the gates of the dam
releases the energy and allows the water
to begin moving. The stored energy turns
into moving energy. This is kinetic energy which is energy of motion.
Whenever work is done, energy is transferred from one object to another. A
boulder resting on top of a cliff has potential energy. The moment the boulder
starts to fall, the potential energy in that rock decreases and the amount of
kinetic energy increases. Though the potential energy is changed to kinetic energy,
the total amount of energy stays the same.
Here are some other changes in energy from one form to another.

Stored chemical energy in a flashlight's batteries becomes light energy when
the flashlight is turned on.

If you overeat, the chemical energy in food is not "burned" but is stored as
chemical energy in fat cells.

A toaster changes electrical energy into heat and light energy. (If you look into
the toaster, you'll see the glowing wires.)

A television changes electrical energy into light and sound energy.
Some transfers of energy are a little more complex.
When an object like a bowling ball is moving down a
lane, it has kinetic energy that can be transferred to
the bowling pins, knocking them down. Where does this
4
kinetic energy come from? It comes from the person rolling the ball. Stored
chemical energy from food eaten by the bowler is converted into moving kinetic
energy, enabling a bowler to do the work of lifting and swinging the bowling ball.
Another more complex transfer of energy starts with our sun and
ends up as our food. Almost all of earth’s energy comes from the
sun. Light energy from the sun is transferred in a variety of ways,
F
providing the Earth with light, heat and other forms of energy.
Plants are able to store energy from the sun through
photosynthesis, the process of using the sunlight to make sugar.
The plant takes in sunlight and combines it with carbon dioxide
from the air and water and minerals from the ground. The sugar
that is made is stored as chemical energy in the leaves, stems and roots of plants.
When humans and other animals eat plants, the potential
chemical energy is released and absorbed by their cells.
Some of the chemical energy from food sources is
converted to energy to help us warm our bodies and some
is converted to mechanical energy that helps us get work
done when we transfer that energy to other objects.
When we eat, our bodies transform the energy stored in
the food into energy to do work. When we run or walk, we
"burn" food energy in our bodies. When we think or read
or write, we are also doing work. Many times it's really hard work!
The burning of fossil fuels such as coal, natural gas, and oil is another example of
energy transfer. Fossil fuels contain chemical energy, a type of potential energy.
When burned, fossil fuels release that potential energy, turning it into heat and
light energy. This chemical energy is sometimes transferred in power plants
mechanically to create electrical energy. The electrical energy is then sent to our
homes and schools and stores. When we turn on a light bulb, this electrical energy
is transferred and released as both heat and light.
Everything you do involves the transfer of energy. From eating to bicycling to
balancing a pencil on your finger, energy conversions are always happening.
5